Rabbit, 155 release kinetics

Another study of stent-based paclitaxel delivery, which also used a degradable polymer [poly(lactide-co-Scaprolactone)] to control the drug-release kinetics, demonstrated sustained reduction in neointimal hyperplasia in the rabbit iliac model (Fg. I I) (56). 

In earlier studies In which macromolecules were released from polymers In vivo (11). the substances tested were proteins or DNA which were metabolized. Thus, a direct comparison of vivo and vitro release was Impossible. We therefore chose the polysaccharide Inulln which has a molecular weight of 5200 daltons. Inulln was chosen as a marker because It Is not metabolized, not excreted by the glomerulus, and Is neither reabsorbed or secreted by the kidney tubules. It Is not bound by plasma proteins and Is not toxic (1. Complete recovery of 3h-inulln (14) or cl -lnulin (15) in urine has been observed from Intravenous Injection Into rats, rabbits, dogs and humans. Thus, Inulln provides an excellent marker for comparing In vitro and In vivo release kinetics because Inulln recovered In urine can be directly compared to Inulln collected In vitro. 

Kim, K., Lam, J., Lu, S., Spicer, P.P., Lueckgen, A., Tabata, Y, Wong, M.E., Jansen, J.A., Mikos, A.G., Kasper, F.K., 2013. Osteochondral tissue regeneration using a bilayered composite hydrogel with modulating dual growth factor release kinetics in a rabbit model. Journal of Controlled Release 168, 166-178. 

The release of steroids such as progesterone from films of PCL and its copolymers with lactic acid has been shown to be rapid (Fig. 10) and to exhibit the expected (time)l/2 kinetics when corrected for the contribution of an aqueous boundary layer (68). The kinetics were consistent with phase separation of the steroid in the polymer and a Fickian diffusion process. The release rates, reflecting the permeability coefficient, depended on the method of film preparation and were greater with compression molded films than solution cast films. In vivo release rates from films implanted in rabbits was very rapid, being essentially identical to the rate of excretion of a bolus injection of progesterone, i. e., the rate of excretion rather than the rate of release from the polymer was rate determining. 

White, H. D., Belknap, B., and Webb, M. R. (1997). Kinetics of nucleoside triphosphate cleavage and phosphate release steps by associated rabbit skeletal actomyosin, measured using a novel fluorescent probe for phosphate. Biochemistry 36, 11828-11836. 

Sustained release intravitreal dexamethasone implants have a potential use in reducing ocular inflammation and treating PVR. The device consists of a 5 mg pellet of dexamethasone coated with 10% PVA and EVA giving a mean release rate of 1.2 0.1 pg/hr over a period of 5 months. A slow release daunomycin implant was fabricated by loading the polysulfone capillary fibre with 1% w/w of daunomycin in tristearin. The controlled release is attributed to the diffusion-retardant properties of the fat. An experimental evaluation of the kinetics and efficacy of this device in a rabbit model at 15 fig and 30 fig/ device resulted in a therapeutically sustained level of daunomycin for up to 21 days after device implantation. Exhausted devices have to be removed surgically, which is an important limitation. 

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